Tübingen Study Sheds Light on the Diet of Carnivores from the Hammerschmiede Hominid Site
The only bear species from the approximately 11.5 million year old Hammerschmiede site in the Allgäu was a relative of the giant panda, but its diet was more similar to the mixed plant-animal diet of today’s brown bears. This was discovered by an international research team from Hamburg, Frankfurt, Madrid and Valencia under the leadership of Professor Madelaine Böhme from the Senckenberg Centre for Human Evolution and Palaeoenvironment at the University of Tübingen when they investigated the eating and living habits of 28 now extinct predator species from the Hammerschmiede. Two publications examining these finds have appeared in the specialist journals Papers in Palaeontology and Geobios.
The Hammerschmiede became known in 2019 through the discovery of the 11.5 million year old ape Danuvius guggenmosi, known as Udo, which was already walking upright. The most recent excavations in the Hammerschmiede under the direction of Madelaine Böhme have revealed an extraordinary diversity of 166 fossil animal species. “Such a thriving ecosystem offers a wealth of ecological niches for the species living in it,” says Böhme. Many of the animals discovered lived both in water and on land or had a climbing lifestyle. “This enabled them to adapt to the forested river that was present in the region at that time,” says the researcher.
What the teeth reveal
The only bear species of the Hammerschmiede, called Kretzoiarctos beatrix, is considered to be the oldest relative of the modern giant panda, as the shape and form of its teeth are similar to those of the Chinese bear, which feeds almost exclusively on bamboo. Kretzoiarctos beatrix was smaller than modern brown bears, but weighed more than 100 kilograms. “In the zoological system, today’s giant pandas are carnivores. In fact, however, they feed exclusively on plants. They have specialized in hard plant food, especially bamboo,” reports Dr. Nikolaos Kargopoulos from the University of Tübingen and the University of Cape Town, the lead author of the new studies. It is scientifically interesting how original carnivores developed an adaptation to such an extreme plant-based diet.
In a first study, the research team investigated the diet of Kretzoiarctos based on the macro and micro morphology of the teeth found. At the macro level, the shape of the teeth changes depending on their role in food processing, which provides information about the general main diet of an animal. At the micro level of the tooth surface, scratches and pits can be seen, caused by contact of food particles with the tooth. “The characteristics of these surface changes can provide information about the feeding habits of an animal during a short period before its death,” says the scientist.
The research team compared the macro- and micromorphology of Kretzoiarctos’ teeth with brown bears, polar bears, South American spectacled bears, and modern and extinct giant pandas. They concluded that the bear from the Hammerschmiede was neither a specialist in hard plants nor a pure carnivore like the polar bear. The diet of the extinct species was more similar to that of a modern brown bear and contained both plant and animal components. “These results are important for our understanding of the evolution of bears and the development of veganism in giant pandas. Kretzoiarctos beatrix, the oldest giant pandas, were therefore generalists. Specialization in the diet of the pandas only occurred late in their evolution,” says Böhme.
The diversity of predators from the Hammerschmiede
In addition to the panda, a further 27 species of predator have been found in the Hammerschmiede so far, the researchers report in a second study. The predators range from tiny, weasel-like animals that weighed less than a kilogram to large hyenas and saber-toothed cats that may have weighed more than 100 kilograms. “Their main diet covers a wide range: There were pure carnivores like the saber-toothed cats, fish eaters like the otters, bone eaters like the hyenas and insect eaters like the civet cat. Some other species such as pandas and martens fed opportunistically on plants and animals of different sizes,” summarizes Kargopoulos. The species discovered also differ greatly in terms of their preferred habitats: “The otter-like animals were good swimmers, bears, hyenas and others stayed on land or lived burrowing like skunks. A particularly large number of species were tree climbers, such as martens, felines, civets and raccoons,” explains the researcher.
“Such a diverse predator population is not only extremely rare in fossils; there is also hardly any modern habitat with such a large number of species,” says Böhme. This biodiversity at the top of the food chain shows that the Hammerschmiede ecosystem must have functioned very well. What’s more, there were even species that existed alongside each other, although they occupied very similar niches, says the researcher. “For example, there were four different otter-like animals of the same size and type of diet. They would normally compete for the natural resources in their environment. But it seems that the Hammerschmiede resources were rich enough to meet the needs of all species.”